Table 2.

Piperidine hit series 2 SAR determined in the human sperm calcium influx assay

Compound	R1	R2	IC50, μM
2a		Cl	7.5 ± 1.3
2b		H	92 ± 14
2c		Cl	18 ± 2
2d			18 ± 7
2e		Cl	> 100
2f		Cl	> 100
2g		Cl	> 100
2h		Cl	> 100*
2i		Cl	> 100*
2j		Cl	87*
2k			> 100*
2l			> 100*

CatSper activated by 3 μM progesterone. IC₅₀ values are means ± SEM of 3 independent experiments.

^*IC₅₀ values are means of 2 independent experiments.